I have checked everything it mentions here and here.
Update: After talking less than five minutes with the Nolting dealer that sold me the machine, problem solved. He had me take a picture of the tension knob and send it to his phone. My thread was running over the tension disks instead of running through it. Awesome service!!! Thanks, Mike from Memory Lane Quilting.
This last picture shows what a knot looks like when I pull on it. It can then be cut. Sometimes it pulls the stitching apart from the front too much and has to be sewn on the sewing machine. I will not do the customer quilts like this. Any suggestions? H E L P!!!